2. They lead to sperm traveling a mile in about the same amount of time as a woman speed walking.
When sperm are first ejaculated, they can reach speeds of up to 28 miles per hour. (This is difficult to measure, says Mark, but that's the most commonly cited top speed.) That's about as fast as Usain Bolt can run. Once they crowd into the vagina, they slow down to about 4 miles per hour -- about as fast as you might walk when you're late to an important appointment. It can take them from 30 minutes to three days to make it all the way to the waiting egg.

3. They won't sabotage his performance in tomorrow's big game.
Athletes and their coaches long believed that getting frisky the night before an event was a bad idea (and they were skittish about testing the hypothesis). The idea was that sex would sap their energy, and for men, that the testosterone expelled during ejaculation could rob them of their mojo. Good news for athletes (and their partners): There's no good scientific evidence that either of these beliefs is true, according to a review of the literature published in the Clinical Journal of Sport Medicine. One study involved a strength test the morning after sex and also after six days of abstinence -- and found no significant difference in the participants' performance. Two other studies concluded that sexual activity had no noticeable effect on grip strength, balance or aerobic power. Some scientists even believe that the male orgasm boosts testosterone, which is good for his general health as well as his game. Keep in mind that these tests didn't measure the psychological effect of sex before sports -- so, no matter what science says, if you think it will slow you down or hold you back, it might.

4. Their byproduct is potent stuff -- but not the way you think.
The average ejaculation consists mostly of a teaspoon's worth of fluid, but only about 2 to 5 percent of that may be sperm. The rest is made up of everything the sperm needs for its long and treacherous journey. Seminal fluid has also been found to contain natural mood enhancers like serotonin, cortisol, prolactin, oxytocin, and estrone, as well as the sleep-aid melatonin. Researchers from the University of Albany raised eyebrows a few years ago when they published a study suggesting that because of semen's unique properties, women who had unprotected sex might be happier than those who had sex with condoms or abstained completely.

5. They don't always require a change of sheets.
You may be surprised to learn that in men, as in women, orgasm and ejaculation are two different processes: One involves the pleasurable, full-body release of tension; the other involves the release of sexual fluid. Most of the time, these events happen simultaneously, but there are cases in which one happens without the other, says Abraham Morgentaler, MD, FACS, a urologist and author of Why Men Fake It: The Totally Unexpected Truth About Men and Sex. Morgentaler says that dry orgasms can be a side effect of alpha blockers prescribed for urinary problems (the medication drastically reduces the release of semen). He's also seen this happen to male patients with diabetes or neurologic conditions, or who had an operation -- for example, to remove their prostate -- that affected the nerves controlling the ejaculatory process. His patients usually describe the feeling as still pleasurable... just less messy.

6. They feel different than yours do.
But not that different! When Canadian researchers asked men and women to fill out a questionnaire with adjectives that described how orgasms felt, both genders said they'd experienced "building," "flooding," "flushing," "throbbing" and "spasms" -- but significantly more men than women in the study also mentioned feeling "shooting sensations."